User's Manual

SARA-R4 series - System Integration Manual
UBX-16029218 - R03 System description
Page 25 of 94
RTS signal behavior
The hardware flow control input (RTS line) is set by default to the OFF state (high level) at UART initialization.
The module then holds the RTS line in the OFF state if the line is not activated by the DTE: an active pull-up is
enabled inside the module on the RTS input.
If the HW flow control is enabled, as it is by default, the module monitors the RTS line to detect permission from
the DTE to send data to the DTE itself. If the RTS line is set to the OFF state, any on-going data transmission
from the module is interrupted until the RTS line changes to the ON state.
The module behavior according to the RTS hardware flow control status can be configured by AT commands
(for more details, see the SARA-R4 series AT Commands Manual [2], AT&K, AT\Q, AT+IFC AT commands).
1.9.1.3 UART multiplexer protocol
SARA-R4 series modules include multiplexer functionality as per 3GPP TS 27.010 [8], on the UART physical link.
This is a data link protocol which uses HDLC-like framing and operates between the module (DCE) and the
application processor (DTE) and allows a number of simultaneous sessions over the used physical link (UART): the
user can concurrently use AT interface on one MUX channel and data communication on another MUX channel.
The following virtual channels are defined:
 Channel 0: Multiplexer control
 Channel 1 – 5: AT commands / data connection
1.9.2 USB interface
1.9.2.1 USB features
SARA-R4 series modules include a High-Speed USB 2.0 compliant interface with 480 Mb/s maximum data rate,
representing the main interface for transferring high speed data with a host application processor, supporting:
 AT command mode
2
 Data mode and Online command mode2
 FW upgrades by means of the FOAT feature (see 1.12.7)
 FW upgrades by means of the u-blox dedicated tool
 Trace log capture (diagnostic purpose)
The module itself acts as a USB device and can be connected to a USB host such as a Personal Computer or an
embedded application microprocessor equipped with compatible drivers.
The USB_D+/USB_D- lines carry USB serial bus data and signaling according to the Universal Serial Bus Revision
2.0 specification [4], while the VUSB_DET input pin senses the VBUS USB supply presence (nominally 5 V at the
source) to detect the host connection and enable the interface. Neither the USB interface, nor the whole module
is supplied by the VUSB_DET input, which senses the USB supply voltage and absorbs few microamperes.
The USB interface is available as AT command / data communication interface only if an external valid USB
VBUS supply voltage (5.0 V typical) is applied at the VUSB_DET input of the module since the switch-on
of the module, and then held during normal operations. In this case, the UART will be not available.
The USB interface is controlled and operated with:
 AT commands according to 3GPP TS 27.007 [6], 3GPP TS 27.005 [7]
 u-blox AT commands (for the complete list and syntax see SARA-R4 series AT Commands Manual [2])
2
For the definition of the interface data mode, command mode and online command mode see SARA-R4 series AT Commands Manual [2]